1. Field of the Invention
The present invention relates to an image forming apparatus and, in particular, to an image forming apparatus for preventing color mismatching, by rotating photosensitive bodies for respective colors in a matched state, and a method for preventing a color mismatch in the image forming apparatus.
2. Description of the Related Art
Known is an image forming apparatus for forming a color image by arranging image forming sections for colors such as yellow (Y), magenta (M), cyan (C) and black (K) near a transfer belt along a running direction of the transfer belt and allowing images based on image data for respective colors to be color matched. The respective image forming section of this apparatus comprises a photosensitive drum, a control section configured to allow a light exposure to be applied to the photosensitive body, a developing agent supply section, and so on. In the image forming apparatus thus formed, it is considered necessary to set the portions of respective drums over a transfer belt and, by drawing lines on the transfer belt with an integral multiple of a circumference length of the drum and detecting the lines, a light exposure timing is controlled to prevent any adverse effect exerted by a rotation vibration on a transfer surface during a rotation of the drum about a drum shaft. By doing so, an image of respective color components is transferred to the transfer belt, avoiding color mismatching.
In the case where, however, a rotation vibration is involved in the photosensitive drum itself, an image interval to be formed on the transfer belt varies during a rotation cycle of the photosensitive drum and there occurs a matched image on the transfer belt at some area but there sometimes arises a color mismatch on the transferred image at other areas. As a result, image quality formed in the image forming apparatus is somewhat lowered.
Therefore, there is a need for an image forming apparatus which prevent an image from being transferred from the photosensitive drum for respective colors onto a transfer surface throughout the rotation cycle of the drum in a color-mismatched state.
According to an aspect of the present invention, there is provided an image forming apparatus comprising photosensitive bodies each rotatable about a predetermined axis and configured to from a color image for respective colors; light exposure sections provided for the respective colors and configured to form a latent image corresponding to a line-like image of a predetermined pitch in an axial direction of the respective photosensitive body; developing sections provided for the respective colors and configured to supply a developing agent corresponding to the respective photosensitive body to allow the latent image which corresponds to the line-like image of the predetermined pitch to be developed; and a transfer belt configured to allow the developed line-like image of a predetermined pitch to be transferred. Further, the apparatus includes sensors each arranged at a predetermined position and configured to detect the presence or absence of any line of the line-like image for the respective colors transferred to the transfer belt, and an adjusting section configured to, based on the phases of waveforms for respective colors calculated from the pitch of the lines which has been detected, relative to the phase of a given photosensitive body adjust the rotation positions of the other photosensitive bodies to allow the phases of the other photosensitive bodies to be substantially matched to the phase of the given photosensitive body.
Objects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention.